We summarize nearly 40 years of research on changes in water yield and timing of streamflow, and over 20 years of stream chemistry data, following conversion of two mixed deciduous hardwood forests to plantations of eastern white pine. Only 10 years after planting, annual streamflow from the pine-covered watersheds was less than expected from mixed hardwoods and by age 15, water yield reductions were about 20 cm. Subsequently, annual streamflow reductions frequently exceeded 25 cm. Significant flow reductions occurred in every month, with the greatest absolute changes in the high flow months and the largest percentage reductions (40%) in the low flow months. Based on hydrologic modelling and experimental data, greater evapotranspiration from pine is due to a much higher leaf area index throughout the year, and, consequently, greater interception loss in the dormant season and more transpiration loss in early spring and late fall. Flow duration analysis showed that conversion to pine reduced the frequency of both high and low flows by 33 to 60 percent. Concentrations of most streamwater solutes were similar between the pine covered watersheds and mature hardwoods. However, nutrient budget comparisons (input-output) showed net accumulations of 1.2 to 4.4 kg ha^-1 yr^-1 for Ca, Mg, K, and Na in pine ecosystems compared to hardwoods. The conservation of nutrients in pine ecosystems is due to reduced discharge and also greater accretion of nutrients in the vegetation compared to hardwoods.